- a boy brought up with another child of different parents.
Origin of foster brother
before 1000; Middle English; Old English fōster brōthor
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for foster brother
"And that's a lie," Gene amended, with the frankness of a foster-brother.Good Indian
B. M. Bower
The E. Your foster-brother will act as your substitute there.
When he died, the care of the property was confided to Jeanbernat, a foster-brother of the Comte.A Zola Dictionary
J. G. Patterson
He was, as I have already written, my father's foster-brother.The Strolling Saint
Nurse's son lives on that common: he was papa's foster-brother.The Fairchild Family
Mary Martha Sherwood